Smart motorways illustrate the some of the consequences of the UK’s two-system measurement muddle. Ronnie Cohen explains.
So-called smart motorways have recently been in the news. Higher numbers of accidents and near misses have been reported on them compared to regular motorways. Smart motorways are motorways without hard shoulders. They use electronic lane displays and technology to track stationary vehicles to warn other drivers. Many claim that they are less safe than regular motorways and that a hard shoulder could have prevented some accidents and near-misses on smart motorways.
On 12 March 2020, the Secretary of State for Transport published a package of 18 measures to improve safety on smart motorways to address the safety problems with smart motorways (source: https://www.gov.uk/government/speeches/strategic-roads-update-smart-motorways-evidence-stocktake). I was disappointed to find that all the measures that involved measurements used imperial units. These are inconsistent with the exclusively metric road design and construction and the exclusively metric emergency marker system.
One of the proposed measures includes “reducing the distance between places to stop in an emergency to three quarters of a mile where feasible so that on future schemes motorists should typically reach one every 45 seconds at 60mph. The maximum spacing will be 1 mile”. They are currently 1.5 miles apart. The DfT gives these measurements in miles but the same DfT gives road contractors all specifications in metric units. These metric units include millimetres, metres and kilometres and can be found in the Traffic Signs Manual.
Another measure is “considering a national programme to install more emergency areas where places to stop in an emergency are more than one mile apart”.
The DfT proposes to install “more traffic signs giving the distance to the next place to stop in an emergency, so you will almost always be able to see a sign. Typically, these will be between approximately 330 and 440 yards apart.”. The DfT could have said “Typically, these will be between approximately 300 and 400 metres apart.”. Why has the DfT decided to yards instead of round numbers of metres?
The use of yards is inconsistent with the emergency marker system. In the emergency marker system, marker posts are placed 100 metres apart and driver location signs 500 metres apart. Both display the number of kilometres from a reference point to help the emergency services to locate stranded drivers. However, only numbers are shown on them. No unit names, abbreviations or symbols are shown to tell drivers what units they are. The emergency marker system exists to benefit drivers but widespread ignorance about this system is probably because they are incompatible with official road signs.
There is another measure to “review existing emergency areas where the width is less than the current 15 foot wide standard. If feasible and appropriate we will widen to this standard.”. This statement obscures the fact that all road features are designed and built exclusively in metric units in accordance with DfT’s exclusively metric specifications to road contractors in the Traffic Signs Manual. Imperial units are only mentioned in the TSM to tell road contractors to put imperial units on road signs for general road users.
I have no doubt that when the DfT updates the Traffic Signs Manual, it will give road contractors the specifications for all these smart motorway features exclusively in metric units with no imperial conversions. The units used in the smart motorway safety measures add more inconsistency and muddle. Once again, it shows the DfT wearing an external imperial mask over an internal hidden metric face. Rip off the mask and it’s all metric underneath. I suspect the mask is just for show. Why do they do this?